Production of hollow ceramic membranes by electrophoretic deposition
First Claim
1. A method of producing a porous hollow ceramic membrane comprising the steps of;
- (a) providing a suspension of a particulate ceramic material having an average particle size greater than about 150 nm in a non-aqueous liquid;
(b) electrophoretically depositing the particulate material onto an electrically conductive fibre core;
(c) drying the fibre core-bearing the deposited material; and
(d) sintering the fibre core bearing the deposited material at a temperature and for a length of time sufficient to combust the fibre core while producing a porous hollow ceramic membrane which has a density less than 95% of the density of the ceramic material.
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Abstract
The present invention provides methods for producing hollow ceramic membranes by electrophoretic deposition. The hollow ceramic membranes may have a small cross-sectional area of about 1.0×10−5 mm2 to about 25 mm2. The cross-sectional configuration of the hollow ceramic membranes may be any geometry such as circular, square, rectangular, triangular or polygonal. The hollow ceramic membranes produced by the methods of the present invention may have multiple layers but always the innermost layer, or the first deposited layer is porous and made by electrophoretic deposition. Subsequent layers may be porous or non porous and deposited before or after sintering the first layer. If it is deposited after sintering, it may require additional sintering steps. Additional layers may be deposited by further electrophoretic deposition, sol-gel coating, dip coating, vacuum casting, brushing, spraying or other known techniques.
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Citations
16 Claims
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1. A method of producing a porous hollow ceramic membrane comprising the steps of;
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(a) providing a suspension of a particulate ceramic material having an average particle size greater than about 150 nm in a non-aqueous liquid;
(b) electrophoretically depositing the particulate material onto an electrically conductive fibre core;
(c) drying the fibre core-bearing the deposited material; and
(d) sintering the fibre core bearing the deposited material at a temperature and for a length of time sufficient to combust the fibre core while producing a porous hollow ceramic membrane which has a density less than 95% of the density of the ceramic material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
(a) the duration and temperature of the sintering step;
(b) the particle size, size distribution and/or the surface area of the ceramic material;
(c) adding the sintering additives in the suspension where additives will deposit concurrently with the ceramic material; and
(d) adding a combustible particulate material to the ceramic material which is concurrently deposited with the ceramic material, wherein said combustible material is removed by combustion during the sintering step.
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11. The method of claim 1 wherein the electrophoretic deposition step is repeated at least once using a ceramic particulate material that is different or has different characteristics such that a multi-layer ceramic hollow membrane where each layer has different characteristics results.
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12. The method of claim 10 wherein the electrophoretic deposition step is repeated at least once using the same ceramic material but having a different particle size distribution and/or surface area such that a multi-layer ceramic hollow membrane having at least two layers having different porosities results.
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13. The method of claim 10 wherein the electrophoretic deposition step is repeated at least once using the same ceramic material but with differing amounts of combustible particles in the suspension to provide a multi-layer ceramic hollow membrane having at least two layers having different porosities.
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14. The method of claim 1 further comprising the step of immersing the fibre core into the particulate suspension once and withdrawing it in a vertical position before re-immersing the fibre core in the particulate suspension for the deposition step.
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15. The method of claim 1 further comprising the step of immersing the fibre core into a liquid once and withdrawing it in a vertical position before immersing the fibre core in the particulate suspension for the deposition step.
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16. The method of claim 1 wherein the non-aqueous liquid is selected from the group consisting of ethanol, methanol, isopropanol, butanol, acetone, butylamine, acetylacetone, methyl ethyl ketone and mixtures thereof.
Specification